Telephone-transmitter



' (Mod 6 J. P. FREEMAN, T. T. 82.11. B. PROSSEB.

TELEPHONE TRANSMITTER.

$10,257,687. V Patented May9, 1882.-

' mum l mu JZZZBSL 7 UNITED STATES PATENT OFFICE.

JAMES P. FREEMAN, TREAT T. PROSSER, AND HENRY B. PRO SSER, OF CHICAGO, ILLINOIS, ASSIGNORS TO THE HOME TELEPHONE COMPANY,

OF ILLINOIS.

TELEPHONE-TRANSMITTER.

SPECIFICATION forming part of Letters Patent No. 257,687, dated May 9, 1882.

' Applicationfiled October 22,1880. (Model) To all whom it may concern Be-it known that we, JAMEs P. FREEMAN, TREAT T. PROSSER, and HENRY B. PROSSER, all citizens of the United States, residing at Ghicago ,in the county of Cook and State of Illinois, have invented certain new and useful Improvements in Telephone-Transmitters; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as willenable others skilled in the art to which it appertains to make and use the same, referencebeing had to the accompanying drawings, and to the letters or figures of reference marked thereon, which form apart of this speci fication.

This invention relates to telephonic transmitters by the vibrations of the diaphragm of which combined intermittent and undulatory 7 electrical currents may be produced in the circuit by a succession of makes and breaks and by variations simultaneously of resistance; and our invention relates more especially to telephonic transmitters in which the variations in resistance are effected by variations in pressure on low conductors, such as carbon buttons.

The object of our invention is to improve telephonic transmitters of this kind with the view of increasing the loudness anddistinctness of articulation of transmitted speech at the receiving end.

To this end our invention consists of a tension regulator compounded of steel filings,

coke, lamp-black, and balsam of fir solidified by pressure; also, of certain novel features of construction, combination, and arrangement of some of the parts of the transmitter, as specifically set forth in claims at the close of this specification.

In order that our invention may be clearly understood, we have illustrated in the annexed drawingsand will proceed to describe the best form thereof at present known to us.

Figure l is a rear elevation of our improved transmitter, showing the induction-coil and a portion of the casein section. Fig. 2 is an axial section of the transmitter.

The same letters of reference are used in both figures in the designation of identical parts.

We use a cylindrical iron case, A, for the support of the various parts of the transmitter,

excepting the diaphragm O, which is supported By the .sheet metal-brass in this instance-havinga nickel-plated front. It is constructed with a rather flat flaring mouth-piece, B. The metallic diaphragm O is fitted in a recess formed in the base-plate of cover B, and is encircled by a U-shaped rubber ring, 0. The diaphragm is held in position by clamping-fingers a, secured to the base-plate of cover B and pressing upon the exterior side of the encircling rubber ring. The center of the diaphragm O is in permanent contact with a platinum point,'d, fixed in a button, D, whichis carried in the ring 0 of a spring arm, E, firmly secured to a hard-rubber bracket, F, fixed on the case A.

Directly behind or in line with the button D is a similar button, Gr, somewhat larger in diameter, however, held in a ring, 11., of a spring-arm, H, firmly secured to a hard-rub ber bracket, I, fixed to case A on the side opposite to that on which bracket F is secured. The buttons D and G constitute the electrodes of alocal battery, the circuit of which includes the primary wire of an electro-magnetic in duction-coil, K, the secondary wire of which extends with one end to the distant station through the telephonic receiver. The buttons D and G may be so adjusted by proper adjustments of their spring-arms that they shall be in permanent contact. So adjusted, the transmission of vocal utterances would be eifected solely by variations of resistance of the circuit consequent upon variations of pressure on the buttons. In practice we find, however, that the best results are obtained when the buttons are adjusted just out of contact, so that transmission may be effected by the combined re sults of successive makes and breaks and variations of resistance. The adjustments of the buttons with respect to the diaphragm and with respect to each other are effected br 2 aaacsr means of adjusting-screws I and I, respectively fitted in tapped holes in metal brackets F and I and bearing with theirpoints against the hard-rubber brackets F and I, which support the spring-arms of the buttons, as heretofore explained. The adjusting-screws are provided withjam-nuts, as usual. The hardrubber brackets are sufficiently elastic to admit of all required adjustment of the buttons.

The end 70 of the primary wire of the induction-coil is electrically connected to the springarm H, while the other end, 70, thereof passes through a hard-rubber eye inserted in the wall of the case, and is in practice connected to one pole of a battery, the other pole of which is connected by a wire, k which also passes through a hard-rubber eye in the wall of the easeto the spring-arm E. The respective ends k and k of the secondary wire of the induction-coil, also passing through hard-rubber eyes in the case, are connected to line and ground, respectively. The exposed portions of these wires within the case may be jacketed with soft-rubber tubes 70", to guard against crosses.

We have discovered that buttons or tension-regulators made of steel filings, coke, and lamp-black saturated with a little balsam of fir and suitably molded under pressure are exceedingly sensitive and more perfect tensionregulators than any we have any knowledge of, and are, withal, very durable.

In order to make a good electrical connection between the button Grand its ring it, we introduce small pieces of platinum foil h between them. The best material for the springarms E and H we have found to be German silver. To guard more effectually against crosses in the induction-coil, we introduce paraffine paper a between the eonvolntions or helices of wire of the same.

With the before-described instrument, the buttons or tension-regulators adjusted just out ()n short lines the induction-coil may be dispensed with altogether.

The supporting-brackets F and 1 may be made of elastic non-conducting material other than hard rubber, although we prefer to use hard rubber.

The diaphragm should be coated with a suitable varnish.

The spring-arm E is made comparatively light and elastic, while the spring-arm H is made much heavier and more rigid.

What we claim as our invention, and desire to secure by Letters Patent, is

1. A tension-regulator composed of a compressed compound of steel filings, coke, lampbla-ek, and balsam of fir, substantially as before specified.

2. The combination, substantially as before specified, of the spring-arm, the button sccured in a ring thereof, and the platinum-foil strips inserted between the button and its encircling ring.

3. The combination, substantially as before specified, of thespring-arm carrying the button or tension-regulator, the rigidly-secured but somewhat elastic non-conducting bracket supporting said arm, and the adjusting-screw acting on-said bracket.

In testimony whereof we affix our signatures in presence of two witnesses.

JAMES P. FREEMAN. TREAT 'l. PBOSSER. H. B. PROSSER.

Witnesses:

H. W. ANDERSON, MARY A. PROSSER. 

